Deletion of the GABA(A) receptor beta 3 subunit eliminates the hypnotic actions of oleamide in mice.

Oleamide (OA) is an endogenous unsaturated fatty acid amide with demonstrated sleep promoting effects in rodents. The sleep enhancing actions of OA may be mediated through interactions with the GABAergic, serotonergic or cannabinergic receptor systems. In this study, we investigated the possible interaction of OA with the GABA(A )receptor by administering OA to mice with a targeted mutation of the GABAA receptor beta 3 subunit (Gabarb3-/-). Peripherally administered OA significantly decreased sleep latency and wake time, while it increased non-rapid eye movement and total sleep times in wild-type (Gabarb3+/+) mice. OA failed to have any sleep-wake effect in Gabarb3-/- mice. On 24 h baseline recordings, no differences between Gabarb3-/- and Gabarb3+/+ mice were observed, indicating that the lack of a pharmacological response to OA in the Gabarb3-/- animals was not secondary to disruptions in physiological. sleep. Therefore, one mechanism by which OA exerts its sleep effects may be through interactions with GABA(A) receptors containing the beta 3 subunit.

The hypnotic actions of the fatty acid amide, oleamide.

Oleamide is an endogenous fatty acid amide which can be synthesized de novo in the mammalian nervous system, and has been detected in human plasma. It accumulates in the CSF of rats after six hours of sleep deprivation and induces sleep in naive rats and mice. Inhibition of the primary catabolic enzyme of oleamide (fatty acid amide hydrolase) by trifluoromethyl-octadecenone reduces sleep latency and increases total sleep time when given centrally to rats and peripherally to mice. While the mechanism of action of oleamide is unclear, it has been demonstrated to increase the amplitude of currents gated by 5-HT2a, 5HT2c and GABAa receptors. Moreover, the action of oleamide most relevant to sleep induction involves, in part, cannabinergic pathways, as evidenced by the ability of the cannabinoid antagonist SR 141716 to inhibit the hypnotic actions of OA. Nonetheless, enhancement of cannabinergic function may not be the only mechanism by which OA alters sleep, as it can act synergistically with subthreshold doses of triazolam (0.125 microg) to reduce sleep latency. These findings raise the possibility that OA may be representative of a group of compounds which might be developed into clinically-used hypnotics, and are discussed in the context of fatty acid derivatives as modulators of neuronal function.

The hypnotic effect of propofol in the medial preoptic area of the rat.

Recent introduction of the intravenous anesthetic propofol as an ICU sedative has allowed a deeply sedated state to be maintained for extended periods in the ICU without delays in emergence. Although such sedation has been advocated to promote physiologic sleep, little evidence exists to support such a strategy. To explore propofol's effect on sleep regulation, we administered propofol directly into the medial preoptic area (MPA) of the rat, an anatomic site where administration of other sedatives (triazolam and phenobarbital) also induce sleep. We performed three two-hour sleep studies in the daytime with the lights on following the administration of propofol (8 ng or 40 ng) or vehicle (intralipid). The higher dose of propofol significantly reduced sleep latency and increased nonREM and total sleep times when compared to vehicle. REM sleep times, intermittent waking times and number of transitions were not altered. Mean nonREM sleep bout length was increased significantly at the higher dose. These findings suggest that propofol may enhance sleep by acting at a hypothalamic site.

Sleep inducing effects of propofol microinjection into the medial preoptic area are blocked by flumazenil.

The intravenous anesthetic, propofol, has been shown to increase sleep when microinjected into the medial preoptic area (MPA) of the rat. Similar increases in sleep have also been observed with triazolam, pentobarbital and ethanol microinjection. Together, these findings implicate the MPA as an important anatomic site mediating the effects of sedatives on naturally occurring sleep. Although the molecular mechanism by which propofol in the MPA acts to induce sleep is unclear, potentiating effects on the GABA(A) receptor complex may play a role. To assess this possibility, we microinjected propofol alone, and in combination with the benzodiazepine receptor antagonist flumazenil, into the MPA. At a dose of 0.76 microg, flumazenil had no effect on sleep when given alone, and completely blocked the increase in sleep caused by a 40-ng dose of propofol although it did not affect the increase in sleep caused by an 80-ng dose of propofol. These data suggest that the sleep inducing property of propofol is in part mediated by direct or indirect actions on the GABA(A)-benzodiazepine receptor complex.

Neurotransmitters and sleep.

Sleep is an active process, not just a default state when there is less incoming sensory information. It can be understood best by considering fluctuating levels of a series of neurotransmitters including the biogenic amines and acetylcholine. The effects of these neurotransmitters are not unique to sleep, but also subserve a wide range of other functions, including affect, sexual behavior, and appetite. The mechanism by which the most common hypnotics work is by binding to the benzodiazepine recognition site of the gamma-aminobutyric acidA-benzodiazepine receptor complex, which mediates action of the most widely distributed inhibitory neurotransmitter in the nervous system. It is possible that some endogenous sleep factors indirectly alter the properties of this receptor complex.

Effects of pinealectomy on baseline sleep and response to sleep deprivation.

STUDY OBJECTIVES: We have previously reported that older (24 mo.) Fischer rats manifest a diminished post-sleep deprivation increase in NREM and REM sleep. In order to examine whether this decline reflects an age-related change in pineal function, we are now reporting on baseline and recovery sleep parameters in pinealectomized 3-, 12-, and 24-month old rats following 24 hours of sleep deprivation using the disk-over-water method. DESIGN: Three independent age groups; within each group there were sequential measures of sleep under baseline conditions and during recovery from sleep deprivation. SETTING: The Sleep Research Laboratory at the University of Chicago PARTICIPANTS: 56 male Fisher (F344) rats INTERVENTIONS: 24 hours of total sleep deprivation using the disk-over-water method MEASUREMENTS: Sleep staging of EEG and EMG, and power spectral analysis of the EEG RESULTS: Pinealectomized (pinex) rats did not differ from sham-operated (sham) rats in total sleep, REM sleep, super-modal high-amplitude NREM sleep (HS2), a measure of NREM EEG delta power, or circadian rhythm amplitude. In the pinex rats, there was a modest (2.5%) age-independent increase in NREM sleep (p<0.02). The pinex rats of all ages failed to manifest the increase in NREM sleep during recovery seen in the sham-operated animals (p<0.04). CONCLUSIONS: We found no evidence that altered pineal function is responsible for age-related changes in baseline sleep in the rat. These data also suggest that, independent of age, normal pineal function may be relevant to the ability to generate increased NREM sleep in response to prior sleep deprivation.

Prolonged sedation with propofol in the rat does not result in sleep deprivation.

UNLABELLED: The use of propofol provides sedation without prolonging emergence in patients in the Intensive Care Unit. When prolonged, however, continuous sedation may overlap with naturally occurring sleep periods and potentially increase the risk of sleep deprivation. We modified an established rat model of sleep to determine whether prolonged, continuous sedation results in sleep deprivation. Rats were continuously sedated for a 12-h period overlapping completely with their normal sleep phase. Electroencephalogram (EEG) and movement data were collected before and after the sedation period. Rats were evaluated for EEG and movement evidence of sleep deprivation after sedation. When compared with baseline, the time spent in rapid eye movement (REM) and non-REM sleep was decreased during the first 4 h after sedation. The duration of non-REM sleep bouts was not altered. Power in the delta band (0.5-4 Hz) during non-REM sleep was diminished during the first 2 h only. Movements were reduced during the first hour after emergence from sedation only. In summary, no EEG or behavioral evidence of sleep deprivation was observed on emergence from sedation. These results imply that sedation is associated with a restorative process reversing the natural accumulation of sleep need that occurs during wakefulness. IMPLICATIONS: Prolonged sedation in the Intensive Care Unit may alter the restorative effects of naturally occurring sleep. We sedated rats during their sleep phase to determine whether sedation interferes with sleep. Upon emergence, no evidence of sleep deprivation was observed. Sedation may thus be associated with a restorative effect similar to sleep.

The relationship of sedation to deliberate self-extubation.

STUDY OBJECTIVES: To evaluate the relationship between sedative therapy and self-extubation in a large medical-surgical intensive care unit (ICU). DESIGN: Retrospective, case-controlled study. SETTING: Large teaching hospital. PATIENTS: All adult patients who underwent unplanned self-extubation during a 12-month period (n = 50). Each patient was matched to two control patients who did not self-extubate based on age, gender, dates in hospital and diagnosis. INTERVENTIONS: none. MEASUREMENTS: Data collected included time to self extubation, dosages and types of benzodiazepines, opioid analgesics, antipsychotics, and hypnotics. Data on the degree of agitation as assessed by nursing staff also were obtained. MAIN RESULTS: When compared to controls, patients in the self-extubation group were more likely to have received benzodiazepines (59% vs. 35%; p < 0.05), but equally likely to have received opioids and/or paralytic drugs. Patients who self-extubated were twice as likely as controls to be agitated (54% vs. 22%; p < 0.05). Use of benzodiazepines was more common in agitated patients than in nonagitated patients (62% vs. 35%; p < 0.02). Among nonagitated patients who self-extubated, increased use of benzodiazepines (57% vs. 29%; p < 0.05) was noted when compared to nonagitated controls. CONCLUSIONS: In intubated ICU patients, benzodiazepines may not consistently treat agitation effectively or prevent self-extubation. Such an effect may be due to paradoxical excitation, disorientation during long-term administration, or differences in drug administration between ICU and operating room (OR) environments.

The sleep-inducing effect of ethanol microinjection into the medial preoptic area is blocked by flumazenil.

Previous studies have shown that a wide range of sedative/hypnotic agents, including ethanol, induce sleep when microinjected into the medial preoptic area (MPA) of the anterior hypothalamus. The mechanism by which ethanol acts at this site to induce sleep has not been clear, though possibilities include alterations of chloride channel function in the GABA(A)-benzodiazepine receptor complex, or increases in neuronal membrane fluidity. In order to explore the former possibility, we have microinjected into the MPA ethanol 0.24 and 0.47 microM, alone and in combination with the benzodiazepine receptor antagonist flumazenil, which has no effects on membrane fluidity or voltage-dependent calcium channel function. Ethanol microinjections significantly reduced sleep latency, and tended (P<0.06) to increase total sleep time. Flumazenil given by itself had no significant effects on sleep, but when given in combination with both doses of ethanol, blocked its hypnotic effects. These data suggest that the sleep-inducing action of ethanol microinjections into the MPA is mediated by ethanol-induced alteration of GABA(A)-benzodiazepine receptor function.

Age-dependent changes in recovery sleep after 48 hours of sleep deprivation in rats.

To characterize possible changes in homeostatic regulation of sleep with aging, we have examined sleep stages during recovery sleep after 48 h of sleep deprivation in young (3 months), middle aged (12 months), and old (24 months) rats. It was found that young and middle aged, in contrast to old rats, had large (21-24%) increases in total sleep time during recovery sleep; the old rats experienced a quantitatively small (8%) but significant rise in total sleep. NREM sleep increased significantly during the recovery period in young and middle aged, but not older rats. High voltage NREM sleep (HS2) declined by 30% during recovery in the young animals, but remained unchanged compared to baseline in the middle aged and old animals. The young and middle aged rats had increases in REM sleep during recovery compared to their baseline by 96% and 93%, respectively, which was significantly greater than a 65% increase during recovery in the old rats. Increases in total sleep and REM sleep during recovery were largely confined to the first 6 h in young and middle aged rats, but maxima for the old rats occurred in the second 6 h.

Depression and sleep disorders: clinical relevance, economic burden and pharmacological treatment.

A wide range of studies have been published over the past two decades that involve the intersection of sleep EEG, insomnia, psychiatric illness (especially depressive disorders) and psychopharmacology. Much of value has been discovered, but there have also been false starts and contradictory results. There is in fact strong evidence that insomnia is associated with medical and psychiatric illness and that the sleepiness associated with insomnia is the cause of many accidents. Thus, the direct (visits to doctors, cost of sleeping medication, complications from use of these medications) and indirect (accidents, quality of life) costs of insomnia are enormous and constitute a major public health problem in the industrialized countries. Believing that it is now timely to assess the state of this important research area, a consensus conference was convened on June 26-28, 1998, in Porto Cervo (Italy) to attempt to clarify the important issues and findings on the clinical effect of the different classes of antidepressant drugs on sleep quality in depression. The participants' consensus on some of the main topics is presented with the hope that this discussion and analysis will contribute to productive research in this important field.

Sleep latency and duration estimates among sleep disorder patients: variability as a function of sleep disorder diagnosis, sleep history, and psychological characteristics.

STUDY OBJECTIVES: Insomnia patients often report greater sleep disturbance than found via polysomnography; yet the specific patient factors related to such sleep time misperceptions are poorly understood. We sought to characterize the extent to which a diverse group of patients complaining of insomnia (n=104) misperceive overnight total sleep time and sleep latency, and to identify patient factors associated with these variations. DESIGN: Cross-sectional. SETTING: University based sleep disorders center. PATIENTS: Sleep disorder groups consisted of patients with psychophysiological insomnia (n=19), sleep state misperception (n=8), insomnia with depressive disorder (n=11), insomnia secondary to Axis I psychiatric disorder other than depression (n=21), periodic limb movement disorder (n=24), and obstructive sleep apnea (n=21). MEASUREMENT AND RESULTS: Patients completed a sleep history questionnaire and the MMPI, underwent overnight diagnostic polysomnographic assessment, and then estimated their total sleep time and sleep latency the subsequent morning. On average, patients overestimated sleep latency, but were equally likely to underestimate vs. overestimate total sleep time. Sleep time misperception was associated with longer periods of wakefulness following sleep onset, greater self-perceived sleep impairment, as well as several psychological dimensions. CONCLUSIONS: Patient factors, including sleep quality, perceptions of habitual sleep time, and current psychopathology, potentially influence sleep time estimation. Whereas psychological factors may lead to exaggeration of sleep disturbance among some patients, sleep quality itself may also influence the congruence between subjective and objective indices of sleep.

Sleep-inducing effects of adenosine microinjections into the medial preoptic area are blocked by flumazenil.

Microinjection of a wide range of sedative agents, including triazolam, pentobarbital, ethanol and adenosine, into the medial preoptic area has been shown to increase sleep, suggesting that it is an important (though not necessarily the only) anatomic site mediating hypnotic effects of these compounds. The mechanism by which adenosine increases sleep at this site is not clear, but one possibility is that this is related to its effects on the GABA(A)-benzodiazepine receptor complex. In order to assess this possibility, this paper describes the administration of adenosine, alone and in combination with the benzodiazepine receptor blocker flumazenil, into the MPA. It was found that 12.5 and 25 nM of adenosine significantly reduced sleep latency and increased total sleep time. The sleep-inducing effect was blocked by flumazenil. Flumazenil caused a modest increase in total sleep, and prevented the increase in total sleep induced by the higher dose of adenosine. These data suggest that at least one aspect of the hypnotic properties of adenosine is mediated by a direct or indirect action on the GABA(A)-benzodiazepine receptor complex.

The hypnotic actions of oleamide are blocked by a cannabinoid receptor antagonist.

The unsaturated fatty acid amide oleamide (OA), which accumulates in the CSF of rats during sleep deprivation, induces electroencephalographically measured sleep when administered intracerebroventricularly. The mechanism of sleep induction by OA is unclear but may derive from enhancements of GABA or 5-HT receptor function, or alternatively from changes in the catabolism or uptake of the related fatty acid amide anandamide, an endogenous cannabinoid-1 (CB1) receptor ligand. The present study tests the latter hypothesis by administering OA alone and in combination with the CB1 receptor antagonist SR141716. As previously reported, 2.8 microg OA administered intracerebroventricularly significantly shortened electroencephalographic sleep latency. SR141716 in a dose of 3 microg had no effects on sleep by itself, but when co-administered with OA prevented its sleep-inducing effects. These data suggest that at least one aspect of the hypnotic action of OA involves interactions with the CB1 receptor system, possibly by blocking the metabolism of the endogenous CB1 receptor agonist anandamide.

Differential rates of psychopathology symptoms in periodic limb movement disorder, obstructive sleep apnea, psychophysiological insomnia, and insomnia with psychiatric disorder.

STUDY OBJECTIVE: To determine patterns and relative intensity of psychopathology, as measured by the Minnesota Multiphasic Personality Inventory (MMPI), in 108 patients with either psychophysiological insomnia (PI; n=20), insomnia with psychiatric disorder (IPD; n=30), periodic limb movement disorder (PLM; n=28), or obstructive sleep apnea (OSA; n=30). DESIGN: Cross-sectional. SETTING: University sleep disorders center. MEASUREMENTS AND RESULTS: Subjects completed the MMPI prior to overnight diagnostic polysomnographic assessment followed by Multiple Sleep Latency Test (MSLT). Seventy five percent of the entire sample had at least one MMPI elevation (T>70). Groups showed significant baseline differences in age, BMI, and MSLT latency (all ps<.05). Logistic regression indicated that even after statistically controlling for these three diagnostic covariates, MMPI elevation was more likely among PLM and IPD patients than OSA or PI patients (all ps<.05). Followup pairwise comparisons indicated that this same pattern of group differences occurred for the Depression, Psychasthenia, and Schizophrenia scales (all ps<.05). CONCLUSIONS: Irrespective of age, obesity, and daytime sleepiness, patients with untreated PLM or IPD are more likely to experience clinically significant psychological difficulties than those with either OSA or PI. These differences are most likely to be manifested in terms of depressive symptoms, anxiety symptoms (tension, worry, guilt), social alienation, and diminished mental concentration. Finally, PLM may be associated with greater MMPI elevations than previously suspected, and agree with earlier clinical reports of high rates of psychiatric treatment in PLM.

Characterization of the hypnotic properties of oleamide.

While preliminary studies associated oleamide with sleep regulation, we now characterize the involvement of oleamide in sleep using a number of techniques. Peripheral administration of oleamide to rats dose dependently suppressed motor activity in the open field, with an ED50 of 17+/-1.5mg/kg for the decrease in distance traveled. Moreover, endogenous oleamide concentrations increased 3- to 4-fold in the cerebrospinal fluid of rats sleep-deprived for 6 h or longer. Oleamide also decreased sleep latency to 44-64% of control values without altering other sleep parameters. Unlike many putative endogenous sleep-inducing agents, oleamide potently induces behavioral and electroencephalographic manifestations of sleep. Moreover, its endogenous concentrations and temporal associations are consistent with previous reports of its enhancement of serotonergic and GABAergic neurotransmission, which may be involved in sleep induction.

A matched comparison of MMPI responses in patients with primary snoring or obstructive sleep apnea.

STUDY OBJECTIVE: To compare the MMPI responses between nonapneic primary snoring (PS) and obstructive sleep apnea (OSA). DESIGN: Cross sectional with matched samples. SETTING: University sleep disorders center. PATIENTS: All PS patients (n = 49) available in a series of 428 clinical referrals to a sleep disorders center, and age and gender-matched OSA patients (n = 49) selected from the 199 available OSA patients in the series. INTERVENTIONS: Not applicable. MEASUREMENTS AND RESULTS: Subjects completed the MMPI prior to overnight diagnostic polysomnographic assessment and multiple sleep latency test (MSLT). OSA patients exhibited a mean of 2.3 elevated MMPI scales, which was significantly more than the PS mean of 1.6 elevations, and attributable to higher OSA scores on Depression (D) and Hypochondriasis (Hs). Approximately twice as many OSA patients than PS patients showed disturbed scores on D (49% vs. 25%, p < .05) and Hy (35% vs. 16%, p < .05). On nine of the ten MMPI clinical scales, both patient groups exceeded the elevation rate expected in nondistressed individuals. Among OSA patients, but not PS patients, number of MMPI elevations had a significant negative correlation with sleep efficiency and average blood saturation during NREM, and a significant positive correlation with wake time after sleep onset. CONCLUSIONS: Compared to patients with PS, those with OSA have more intense depressive symptoms (e.g., pessimism, inactivity, guilt) and somatic concerns. General psychopathology is associated with blood oxygen saturation only among OSA patients. Nonetheless, PS patients show psychological maladjustment that is qualitatively similar, but quantitatively less severe, than that characterizing OSA.

MMPI correlates of sleep and respiratory disturbance in obstructive sleep apnea.

STUDY OBJECTIVE: To evaluate associations between polysomnographic variables in obstructive sleep apnea (OSA) and a variety of psychological responses (including depressive symptoms) as assessed by the Minnesota Multiphasic Personality Inventory (MMPI). DESIGN: Cross-sectional. SETTING: University sleep disorders center. PATIENTS: One-hundred seventy eight consecutive clinical OSA patients. INTERVENTIONS: Not applicable. MEASUREMENTS AND RESULTS: Patients completed the MPI prior to overnight diagnostic polysomnography. Fifty-eight percent demonstrated at least one MMPI elevation (mean = 1.8 elevations), with Depression (D) elevated for 32%, Hypochondriasis (Hs) for 30%, and Hysteria (Hy) for 21%. Thirty-eight percent demonstrated two or more elevations, with several variations of Hs-D and Hs-D-Hy configurations evident. "Conversion V" profiles were fairly rare, and a large number of miscellaneous configurations occurred once. Significant correlations were detected between several MMPI scale scores and total sleep time, the apnea-hypopnea index (AHI) during REM, and particularly arterial oxygen saturation, even when partialling out variance related to body mass index (BMI). In contract, D scores were not correlated with any polysomnographic parameters. Based upon MMPI configuration, the sample was subdivided into the following seven profile groups: Nonelevated (n = 74); Single D (n = 11); Single non-D (n = 25); Combined D plus (a) HS or HY (n = 7), (b) Hs and Hy (n = 10), or (c) other (n = 29); and Multiple non-D (n = 22). Multivariate analysis controlling for age and gender indicated higher AHI in the Single non-D, Combined D plus other, and Multiple non-D groups, compared to the Single D group. Also, there was lower average oxygen saturation in the Multiple non-D group, compared to Single D, Single non-D, and Nonelevated groups. The Combined D plus HS and/or Hy groups did not differ from each other or from other groups, even when merged. The Multiple non-D findings were unattributable to any specific scale or overall number of elevations. CONCLUSIONS: OSA patients who have core depressive symptoms (as measured by MMPI scale D) without significant psychological symptoms in other areas tend to have less severe OSA, whereas those with a diverse set of other psychological symptoms overshadowing depressive symptoms (e.g., somatic focus, emotional reactivity, family/marital problems, cognitive problems, etc.) tend to have greater AHI and lower oxygen saturation. Although it seems probable that these MMPI differences primarily reflect OSA effects, prospective research is needed to confirm this hypothesis.

Age-related changes in sleep in the rat.

Human sleep in old age is characterized by a number of changes, including reductions in sleep efficiency, amounts of visually scored slow-wave and REM sleep, and amplitude of the diurnal sleep/wake rhythm. In older rats, some, but not all, of these traits have been reported, including a decrease in the mean duration of sleep bouts, an increase in the number of sleep bouts, and a modest reduction of REM sleep. Studies of the diurnal rhythm of total sleep have had varied results. There are, however, virtually no data indicating at what point across the rat's lifetime the changes seen in old age begin to occur. In order to more fully characterize sleep in older rats, and to develop data on when they first appear, we have examined sleep in young adult (3 months), middle-aged (12 months), and older (24 months) rats during 24 hours under constant dim light. Analyses of variance revealed no age-related changes in total sleep, NREM or REM sleep, wake time after sleep onset, or three different measures of the amplitude of the sleep/wake circadian rhythm. There were, however, significant age-related reductions in high-voltage NREM sleep ("HS2"), the mean length of sleep bouts, and REM-onset duration. These were seen in the 1-year-old rats, indicating that the changes seen in the older animals were evident by midlife.

Effects of microinjections of triazolam into the ventrolateral preoptic area on sleep in the rat.

In view of interest in the ventrolateral preoptic area (VLPO), based on FOS protein accumulation during sleep as well as its output pathways to areas involved in sleep regulation, we have examined the effects of microinjections of triazolam into the VLPO. It was found that two doses of triazolam, noted previously to enhance sleep when injected into the medial preoptic area, had no significant effect on sleep or core temperature when administered into the VLPO. Although these data do not bear on the possibility that the VLPO is involved in physiological sleep regulation, they suggest that it is not a site of the pharmacologic action of hypnotic benzodiazepines.